The Royal Pod is a lotus bulb chosen by Queen Tara as the best candidate to receive and contain The Life of the Forest. It's purpose is to hold this power until blooming at which point it releases the magic onto the chosen heir. If this is done in moonlight, it gives its power to the chosen heir of the queen of the forest. If it blooms in darkness, the heir will be the next king of rot.
The Pod was a mystery to the heroes through most of the movie as without the queen, no one had all the information on its care. Mub and Grub knew that it had to be kept moist, Nin Galuu's tree held a scroll that said similar and that it must bloom in the light of the moon. The rest of the scroll was stolen by Mandrake and he was the only one to know that if the pod would bloom in darkness, it would become his dark prince, though it's not clear what that process would be like.
Plot[]
The pod was one of the many raised by the keepers Mub and Grub. When Queen Tara arrived to pick her royal pod, the keepers offered her their biggest but the queen was drawn to the tinier pod for reasons she did not explain. Grub handed it to her and Tara cradled the pod which began wrapping it's roots around her fingers, coming alive. She proclaimed this to be her chosen pod, showing it to all in assembly.
It was at this point that the boggin army launched their attack and Tara was forced to flee through the forest with the pod. She protected it against the army and almost escaped with Ronin but was struck down by one of Mandrake's rot arrows which sent her falling into the forest, There, she was found by Mary Katherine and made the decision to entrust her with the pod, placing the last of her magic into it so that it would shrink the girl down to leafmen size. Tara instructed her to take the pod to Nim Galuu and just as Ronin found them, she died in his arms. Ronin understood the necessity to care for the royal pod but since they had no information about it without Tara, he was tasked with escorting Mary Katherine (plus Mub and Grub) to Nim Galuu.
After picking up Nod and escaping a few dangers, they eventually reached Nim Galuu's tree, where all the knowledge of the forest was kept. They found information about caring for the royal pod, that it must be kept moist and that it must bloom in the light of the full moon. But half of the scroll was missing. Mary Katherine also learned that Tara had placed an additional spell on the pod so that if she stayed with it until it blossomed, she could return to full height. All were pleased with what they've found and Mub and Grub took charge of the pod.
With Ronin, Nod, and M.K. distracted, Mandrake stormed Nim Galuu's tree and took the pod, plus the slugs, back to his land. There, he explained his plan to have the pod bloom in darkness so that it would become his new prince of rot, information he obtained from the part of the scroll he'd stolen. He locked the slugs into a dark hole where they were to care for the pod until it bloomed.
The slugs and pod are rescued by the others and taken to Moonhaven. However, Mandrake deploys his backup plan of using bats to block the moon so the leafmen must try to scatter them, to little success. Mandrake infiltrates the blossoming room to claim the Pod but is pushed back by Ronin and Nod. Meanwhile, M.K. led her father, Professor Bomba, to Moonhaven so that he could help. Using his recording of bat sounds, he drew the bats away and cleared the skies. The pod was able to bloom in the moonlight and unleashed its power, banishing Mandrake from Moonhaven and locking him into a gall on a tree where he would never escape.
The pod was allowed to bloom in full, releasing the contained magic of the forest as well as the remaining spirit of Tara. After searching across the room, it settles upon the "Flower Child" Jinn who Tara had met when she was still alive. The spirit of Tara asked her to watch over the forest and finally bestowed her blessing on the girl, crowning her the new queen and instilling in her the Life of the Forest.